Optical instruments such as endoscopic imaging devices have been used in medical applications for many years. A common technique for performing minimally invasive imaging involves placement of the imaging device inside a catheter, such as a central venous catheter, which then carries the imaging device to a desired intravenous location. Due to space constraints encountered when inserting these devices into a patient, the size of the imaging transducer is designed to be as small as possible. Thus, electronic components used to process transducer signals are located remotely from the catheter and are typically coupled to the transducer by running cable or optical fiber through the catheter.
To ensure a good connection between connecting ends of an optical fiber, connectors are typically designed with cylindrical ferrules suspended within a connector body. A typical fiber optic connector 10 is shown in FIG. 1. The ferrule 12 is bored through the center at a diameter that is slightly larger than the diameter of the fiber 14. The fiber 14 is then fed through the ferrule 12, so that the end of the fiber 14 coincides spatially with the end of the ferrule 12. During coupling, the ferrule 12 guides the end of the fiber 14 into an alignment sleeve 16 of a mating receptacle 18. A locking mechanism 20 may be formed on the outside of the receptacle 18 and the connector body 22 to hold the mated pair securely together. Because the diameter of the fiber 14 may be on the order of 10 μm, very tight dimensional tolerances are required for those components of the connector assembly that are responsible for aligning the fibers.
The locking mechanism 20 is typically a bayonet type connection, a threaded sleeve connection, or other locking device that prevents the mated ends from becoming uncoupled in the presence of a pulling force or tension across the connection. The locking mechanism 20 helps to maintain proper alignment of the mating ends of the fiber 14 to minimize insertion loss across the connection. The locking mechanism 20 also helps to ensure the integrity of the optical transmission path when the connection is under tension. Locking connectors may be critical for applications such as telecommunications, security, and other data transmission systems that require very high reliability.
In medical applications, however, it may not be desirable to maintain a locked connection, even in the presence of tension across the connection. This is especially true in the case of an imaging device or other measuring device or sensor that is inserted into a patient through an intravenous catheter. For example, when an electronics module or instrument rack connected to the catheter leads is moved or falls over, it can pull the catheter leads with it. Excessive tension placed on the catheter leads or other connective cable may cause considerable discomfort to the patient, displacement of the catheter, or in the worst case, removal of the catheter from the patient access site.